The biosynthesis of a large number of monoterpenes in the corresponding production organisms has already been elucidated. Frequently, linear precursor molecules are cyclized by highly-specific biocatalysts. The precursors are, as a rule, esters of linear terpene alcohols and diphosphoric acid. A typical example of such a precursor is geranyl pyrophosphate. The pyrophosphate group is enzymatically eliminated from the molecule and subsequently hydrolyzed to give two phosphate ions. This gives rise on the other side to a carbo cation, which is now capable of undergoing further intramolecular reactions and recombines to give a cyclic monoterpene, for example with elimination of a proton (Curr. Opin. Chem. Biol. 2009, 13:180-188).
As, is known, non-activated triterpenes such as squalene or oxidosqualene are reacted in vivo by squalene-hopene cyclases (SHC) to give the corresponding cyclic compounds (Siedenburg, G. and Jendrossek, D., Applied and Environmental Microbiology, 2011, 77, (12), 3905).
The activity of certain squalene-hopene cyclases (SHC) is not limited to triterpenes. The international application PCT/EP2011/070304 (WO 2012066059 A2), the disclosure of which is herein expressly incorporated by reference in its entirety, describes squalene-hopene cyclase mutants which catalyze the cyclization of a citronellal isomer to an isopulegol isomer.
The international application PCT/EP2010/057696 (WO 2010139719 A2), the disclosure of which is herein expressly incorporated by reference in its entirety, proposes squalene-hopene cyclases as biocatalysts for the cyclization of homofarnesol to ambroxan.
The gene and protein sequences of the squalene-hopene cyclase from the bacterium Zymomonas mobilis (Zm-SHC) are known (Genpept Accession No AAV90172 2004 and Nat Biotechnol 2005, 23:63-68, cf. SEQ ID No. 1 and 2).
Object of the present invention was to provide a process for the cyclization of geranyllinalool.